Obama is expected to make the announcement Friday afternoon at the White House, the official said. Johnson would succeed Janet Napolitano, who left in July to become president of the University of California system.

In choosing Johnson, Obama is promoting the lawyer known for leading the way on reforms to the military commissions system at the Guantanamo Bay prison. Johnson also helped to write the report that led to the repeal of the “Don’t Ask, Don’t Tell” policy forbidding gays in the military from disclosing their sexual orientation.

Obama is nominating Johnson because he is “one of the most highly qualified and respected national security leaders,” the White House official said in an emailed statement.

Johnson, who is African American, would join two other black members of the president’s cabinet, Atty. Gen. Eric Holder and Transportation Secretary Anthony Foxx.

While at the Department of Defense, Johnson was responsible for the prior legal review and approval of every military operation approved by the president and the Defense secretary, according to the White House.

After leaving the Pentagon in January, Johnson returned to the Washington offices of the Paul Weiss law firm, where he began his career. He has also served as a federal prosecutor.

From the congressional halls to the Jersey shore, here's a look at the best photos surrounding the year's political discourse in 2013. Read more: Debate over the Affordable Care Act. Timeline: Politics in 2013.

WASHINGTON -- President Obama lectured members of Congress on Thursday on their responsibility to serve the country, urging them to negotiate with him on the budget and immigration reform instead of endangering the country with games of "brinkmanship."

WASHINGTON -- John A. Boehner has found his options limited during his three years as House speaker by an informal rule for Republicans that dictates he move only legislation that has the approval of a majority of support among his own membership.

WASHINGTON -- Vice President Joe Biden rolled out the welcome mat to returning Environmental Protection Agency workers furloughed during the 16-day shutdown, offering muffins and his hope that Washington can avoid a repeat of the budget battle in three months.

Interim Baltimore Police Commissioner Kevin Davis announced a reorganization of the department in an email to police Saturday night, formally promoting or moving 28 people into new roles and undoing some changes made by his predecessor Anthony W. Batts.